EP0572368A2 - Système à matrice de capteurs capacitifs discriminateur de phase - Google Patents

Système à matrice de capteurs capacitifs discriminateur de phase Download PDF

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Publication number
EP0572368A2
EP0572368A2 EP93850112A EP93850112A EP0572368A2 EP 0572368 A2 EP0572368 A2 EP 0572368A2 EP 93850112 A EP93850112 A EP 93850112A EP 93850112 A EP93850112 A EP 93850112A EP 0572368 A2 EP0572368 A2 EP 0572368A2
Authority
EP
European Patent Office
Prior art keywords
sensor
phase
adjustment made
voltage
sensor signal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP93850112A
Other languages
German (de)
English (en)
Inventor
John M. Vranish
Wadi Rahim
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
US Department of Health and Human Services
National Aeronautics and Space Administration NASA
Original Assignee
US Department of Health and Human Services
National Aeronautics and Space Administration NASA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by US Department of Health and Human Services, National Aeronautics and Space Administration NASA filed Critical US Department of Health and Human Services
Publication of EP0572368A2 publication Critical patent/EP0572368A2/fr
Withdrawn legal-status Critical Current

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
    • G01D5/14—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage
    • G01D5/24—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying capacitance
    • G01D5/2405—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying capacitance by varying dielectric
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
    • H03K17/94—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the way in which the control signals are generated
    • H03K17/945—Proximity switches
    • H03K17/955—Proximity switches using a capacitive detector
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
    • H03K17/94—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the way in which the control signals are generated
    • H03K17/96—Touch switches
    • H03K17/962—Capacitive touch switches
    • H03K17/9622—Capacitive touch switches using a plurality of detectors, e.g. keyboard

Definitions

  • This invention relates to a phase discriminating capacitive sensor array system producing sensor signals which are phase and amplitude controlled based on a frequency reference provided by a single frequency stabilized oscillator.
  • Capacitive sensor arrays are used in industry to sense the proximity of an object.
  • capacitive sensor arrays have been provided with a circuit having a number of free running oscillators, each corresponding to one of a number of sensor elements in the array provided to sense the object.
  • the corresponding oscillator experienced a change in frequency.
  • the conventional circuit recognized the object based on a change in capacitance caused by the change in the frequency of the free running oscillator.
  • each of the free running oscillators provided for each sensor element is susceptible to being "pulled” as described above, the sensors must be placed far enough apart to ensure that the free running oscillators in each sensor do not interact, couple and lock on to each other (cross talk).
  • the range and sensitivity of the conventional system has been limited by a significant degree.
  • pixelized imaging has not been possible due to the lack of proximal collocation of the sensor elements.
  • Another disadvantage of the conventional capacitive sensor array system has been that the multiple free running oscillators have required that relatively wide band widths be provided for the sensor electronics input bandwidths. These wide bandwidths have resulted in increased noise and a decreased signal-to-noise ratio. As a result of this disadvantage as well, the range and sensitivity of the conventional system have been limited by a significant degree.
  • Another object of the invention is to provide a capacitive sensor array system with narrow band filtering and resulting minimal noise and high signal to noise ration, without frequency drift, and which can detect the proximity, closing speed and edges of an object sensed by the sensor elements.
  • phase discriminating capacitive sensor array system which provides a single free running oscillator which is stabilized to a fixed frequency.
  • Multiple sensor elements are provided for which the single oscillator is a frequency reference.
  • Multiple phase control units corresponding to the multiple sensor elements, are also provided which control the phase and amplitude of the sensor signals from the sensor elements to stay identical to that of the frequency reference, and which determine the proximity of an object by measuring the adjustment made to the sensor signals.
  • the phase control units may also determine the closing speed of the object based on the rate of change of the adjustment, and the edges of the object based on a sudden reduction in the adjustment made.
  • FIG. 1 shows an overall block diagram of the phase discriminating capacitive sensor array system of the invention, having an array 2 comprised of a common shield 4 on which sensor elements 1-N are provided, and a common ground 6.
  • the shield 4 and sensor elements 1-N each output a sensor signal to N phase control units 8, 10, 12, 14 and 16-18, respectively.
  • Each phase control unit maintains the phase and amplitude of the sensor signal from each of the sensor elements 1-N, in accordance with a frequency reference provided by a crystal controlled oscillator 20.
  • the oscillator is frequency stabilized to a common frequency shared by the shield 4, ground 6 and sensor elements 1-N.
  • the phase control units each produce an output signal (denoted shield output, and outputs 1-N). These output signals represent the voltage required to keep the sensor signals provided by the corresponding sensor elements 1-N at the same frequency, phase and amplitude.
  • FIG. 2 is a block circuit diagram of any one of the phase control units 8, 10, 12, 14, and 16-18.
  • the phase control unit 10 which controls the sensor signal from sensor element 1, and produces output 1, is shown.
  • the frequency reference from the oscillator 20 is passed through a conventional phase shifter 22 and then through a conventional gain control 24.
  • the output of the gain control drives a conventional resistor 26 connected to the sensor element 1 and the input of a conventional buffer amplifier filter 28.
  • the buffer amplifier filter 28 includes a narrow bandpass filter at the frequency reference in order to remove a significant amount of the ambient noise. Since the frequency is fixed, the bandwidth is only as wide as the motion of the object sensed by sensor 1, for example, 2 hertz. The narrow band filtering is possible because the sensor element simply appears as part of an impedance in a transmission line. This filtering occurs upon input of the sensor signal to the phase control unit.
  • the output of the buffer amplifier filter 28 drives a conventional phase comparator 30 and level comparator 32.
  • the outputs from these comparators are input to a controller 34, which drives the phase shifter 22 and gain control 24 to maintain the signal from sensor 1 identical to the frequency reference from the oscillator 20.
  • the sensor element 1 When the sensor element 1 senses an object, its change in capacitance changes the amount of adjustment required to be made by the controller 34 to the sensor signal. This change in the required amount of adjustment is reflected by a corresponding change in voltage in the output signal (output 1) from the controller 34. Thus, the change in voltage in output 1 indicates the proximity of the object sensed by sensor 1. Also, the rate of change in this voltage, which reflects the rate of change in the required amount of adjustment, thus indicates the closing speed of the object.
  • FIG. 3 is the flow chart of the control performed by the controller 34.
  • the controller voltage V AMP used to set the initial voltage at the sensor element
  • the controller voltage V PH used to set the initial phase at the sensor element
  • the change in voltage ⁇ V, and the change in phase-induced voltage ⁇ PH which are expected to result when the sensor element encounters the object, are initialized based on an initial estimate for these values as expected.
  • the amplitude AMP of the sensor signal is compared to the controller voltage V AMP which indicates the initial sensor voltage.
  • V AMP exceeds V AMP
  • the controller voltage V AMP is adjusted in step 40 by adding the change in voltage ⁇ V of the sensor signal caused by the capacitance change in the sensor element when the sensor element senses an object. If, however, AMP does not exceed V AMP then V AMP is adjusted in step 42 by subtracting the change in voltage ⁇ V.
  • step 44 the phase PH of the sensor signal is compared to controller voltage V PH (which indicate the initial sensor phase). If PH exceeds V PH then the controller voltage V PH is adjusted in step 46 by adding the phase induced voltage change ⁇ PH. If, however, PH does not exceed V PH then V PH is adjusted in step 48 by subtracting ⁇ PH.
  • step 50 ⁇ V and ⁇ PH are then recomputed based on a software search which implements in iteration to converge these values to within a specified range.
  • the specified range takes into account the distance and speed of the object.
  • step 52 the controller voltages V AMP and V PH are output as the output signal indicating the proximity and closing speed of the object. Control then returns to step 38, and the above described steps 38-52 are continually repeated as appropriate.
  • the sensor elements 1-N can be placed as closely together as desired, so that cross talk between the sensor elements is eliminated.
  • the proximity and closing speed are measured by the adjustment made to the sensor signals for each sensor element, instead of by measuring an effect on a free running oscillator for each sensor element, as in the conventional capacitive sensor array system described above in the Background of the Invention.
  • multiple free-running oscillators do not need to be provided corresponding to the multiple sensors, and cross-talk is therefore not a problem.
  • the sensor elements can be placed as closely to the shields as desired in a "capaciflector" system, as described above.
  • the sensor elements 1-N can be provided on the single shield 4 as shown in FIG. 2.
  • the output signals which provide the voltage indicative of the proximity and closing speed of the object can be provided to a robot controller which interprets and acts on the proximity and speed information accordingly.
  • a pixelized image of the object can be produced using the output signals (shield output and outputs 1-N).
  • the edges of the object can be detected based on a sudden decrease in the voltages indicated by the output signals, which indicates a fall off of the amount of adjustment applied to the sensor signals for the sensor elements sensing the object at the edge.
  • output signals providing the voltages indicative of the proximity, closing speed and edges of an object can be utilized in a number of applications including but not limited to the robotics sensing and pixelized imaging described above.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Electronic Switches (AREA)
  • Geophysics And Detection Of Objects (AREA)
  • Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)
EP93850112A 1992-05-28 1993-05-24 Système à matrice de capteurs capacitifs discriminateur de phase Withdrawn EP0572368A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US889577 1992-05-28
US07/889,577 US5214388A (en) 1992-05-28 1992-05-28 Phase discriminating capacitive array sensor system

Publications (1)

Publication Number Publication Date
EP0572368A2 true EP0572368A2 (fr) 1993-12-01

Family

ID=25395396

Family Applications (1)

Application Number Title Priority Date Filing Date
EP93850112A Withdrawn EP0572368A2 (fr) 1992-05-28 1993-05-24 Système à matrice de capteurs capacitifs discriminateur de phase

Country Status (4)

Country Link
US (1) US5214388A (fr)
EP (1) EP0572368A2 (fr)
AU (1) AU646200B2 (fr)
CA (1) CA2096174A1 (fr)

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Publication number Priority date Publication date Assignee Title
EP0838737A1 (fr) * 1996-10-25 1998-04-29 Asulab S.A. Dispositif d'identification d'une action manuelle sur une surface, notamment pour une pièce d'horlogerie
EP0984329A2 (fr) * 1998-09-04 2000-03-08 Canon Kabushiki Kaisha Appareil pour la détection de la position ayant une pluralité de sections de détection et appareil d'exposition
WO2003106936A2 (fr) * 2002-06-13 2003-12-24 Environment One Corporation Capteur de reseau capacitif a balayage et procede associe

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US6498471B2 (en) 1999-05-04 2002-12-24 A. Clifford Barker Apparatus and method for direct digital measurement of electrical properties of passive components
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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0838737A1 (fr) * 1996-10-25 1998-04-29 Asulab S.A. Dispositif d'identification d'une action manuelle sur une surface, notamment pour une pièce d'horlogerie
FR2755269A1 (fr) * 1996-10-25 1998-04-30 Asulab Sa Dispositif d'identification d'une action manuelle sur une surface, notamment pour une piece d'horlogerie
US6184871B1 (en) 1996-10-25 2001-02-06 Asulab S.A. Identification device of a manual action on a surface, in particular for a timeplace
EP0984329A2 (fr) * 1998-09-04 2000-03-08 Canon Kabushiki Kaisha Appareil pour la détection de la position ayant une pluralité de sections de détection et appareil d'exposition
EP0984329A3 (fr) * 1998-09-04 2002-05-02 Canon Kabushiki Kaisha Appareil pour la détection de la position ayant une pluralité de sections de détection et appareil d'exposition
US6529263B2 (en) 1998-09-04 2003-03-04 Canon Kabushiki Kaisha Position detection apparatus having a plurality of detection sections, and exposure apparatus
US7072023B2 (en) 1998-09-04 2006-07-04 Canon Kabushiki Kaisha Position detection apparatus having a plurality of detection sections, and exposure apparatus
WO2003106936A2 (fr) * 2002-06-13 2003-12-24 Environment One Corporation Capteur de reseau capacitif a balayage et procede associe
WO2003106936A3 (fr) * 2002-06-13 2004-06-17 Environment One Corp Capteur de reseau capacitif a balayage et procede associe

Also Published As

Publication number Publication date
US5214388A (en) 1993-05-25
AU646200B2 (en) 1994-02-10
CA2096174A1 (fr) 1993-11-29
AU3853793A (en) 1993-12-09

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